<template>
<ul class="list">
	<li class="item" v-for="item of letters" :key="item" @click="handleLetterClick" @touchstart="handleTouchStart" @touchmove="handleTouchMove" @touchend="handleTouhEnd">{{item}}</li>
</ul>
</template>

<script>
export default {
	name: 'CityAlphabet',
	props: {
		cities: Object
	},
	data () {
		return {
			touchstatus: false,
			startY: 0,
			timer: null
		}
	},
	computed: {
		letters () {
			const letters = []
			for (let i in this.cities) {
				letters.push(i)
			}
			return letters
		}
	},
	update () {
		this.startY = this.$refs['A'][0].offsetTop
	},
	methods: {
		handleLetterClick(e) {
			this.$emit('change',e.target.innerText)
		},
		handleTouchStart () {
			this.touchstatus = true
		},
		handleTouchMove (e) {
			if(this.touchstatus){
				if (this.timer) {
					clearTimeout(this.timer)
				}
				this.timer = setTimeout(()=>{
					const touchY = e.touches[0].clientY-79
					const index = Math.floor((touchY-this.startY)/20)
					if (index>=0 && index<= this.letters.length){
					this.$emit('change',this.letters[index])
					}
				},8)				
			}
		},
		handleTouhEnd () {
			this.touchstatus = false
		}
	}
}
</script>

<style lang="stylus" scoped>
@import '../../../assets/styles/varibles.styl'
.list
	position: absolute
	top: 1.58rem
	right: 0
	bottom: 0
	width: .4rem
	display: flex
	flex-direction: column
	justify-content: center
	.item
		text-align: center
		line-height: .4rem
		color: $bgColor	
</style>